The present invention relates generally to locks and more particularly to a padlock with an alarm which operates when someone tries to violate or tamper with the padlock.
Generally, a padlock comprises a body and a shackle having long and short legs. The shackle is mounted for reciprocal movement relative to the body between a closed, depressed position in which both legs are in the body and an extended, open position in which the short leg is outside the body. Located within the body is a latch for engaging one leg of the shackle when the shackle is in its closed position, and this prevents movement of the shackle to its open position. In order to move the shackle from its closed to its open position, the latch must be disengaged, and the padlock includes a lock mechanism operable to disengage the latch. The lock mechanism may be key operated or combination-operated in an authorized manner. The padlock is typically composed of a hard metal such as steel.
Padlocks are used for securing possessions or property to prevent theft or trespassing. It is not uncommon, however, for someone intent on theft or trespassing to tamper with the padlock in an attempt to open it in an unauthorized manner, either by severing the shackle or by forcing it into an open position or the like. To deter a thief or the like from tampering with the padlock, it has been proposed in the past to provide the padlock with an integral alarm system which sounds an alarm when the thief violates or tampers with the padlock.
A padlock having an integral alarm system is disclosed in Stevens, U.S. Pat. No. 3,993,987. Such a system conventionally includes, in addition to the audible alarm sounding device, a battery for energizing the audible alarm sounding device and an electrical circuit having switches connecting the audible alarm sounding device to the battery for actuating the audible alarm sounding device when a violation occurs or an attempt is made to tamper with the padlock.
Because such an alarm system is powered by a battery, and because a battery can die, one should be able to test the battery to determine whether it still has sufficient power to operate the alarm. Provision for testing the battery is made in the system disclosed in the above-noted Stevens patent, but the test is complicated, bothersome and otherwise undesirable.
Moreover, because all batteries eventually wear out and must be replaced, access must be provided to the battery within the padlock to permit removal and replacement of the battery. Such a provision, however, gives a thief the opportunity to gain access to the battery to remove it and deactivate the alarm.
In addition, in Stevens, there is no special provision for sound emission from the padlock when the audible alarm sounds.